OK, just done a quick scan of the thread, but your problem may be the "intelligent" channel selection algorithms on the sagecom router. It will dynamically change your wifi channel, no matter what your router is set to, "auto" or your specific chosen channel. That is why your channel changes from your selection.
Quite a few people having problems with this router feature which does occasionally seem to pick the "worst" channel rather than the "best". Widely reported on the TT Community Forums.
You need to get in touch with TalkTalk to have this switched off.
Edited by iefbr14 (Fri 01-Jan-21 17:21:47)